1. Field of the Invention
This invention relates to nonwoven surface finishing articles comprising a three-dimensional web of polyester fibers which are bonded together with a phenol-formaldehyde resin. The invention also relates to a method of making the articles involving UV irradiation of the polyester fibers before application of the bonding resin.
2. Description of Related Art
Nonwoven, three-dimensional, fibrous, abrasive products have been employed to remove corrosion, surface defects, burrs and impart desirable surface finishes on various articles of aluminum, brass, copper, steel, wood and the like. Nonwoven, three-dimensional fibrous products made according to the teaching of U.S. Pat. No. 2,958,593 have been widely used for some time. Typically, a nonwoven, three-dimensional web of fibers is coated with a resin. The resin may optionally contain an abrasive Many combinations of staple fibers, resinous binders, and optional abrasive particles have been employed in these products. One particular fiber and resin combination which has gained widespread use is nylon 6 or 66 fibers with thermoset phenol formaldehyde resins coated thereon. However, a drawback of using nylon fibers in surface finishing products is the relatively high cost of nylon as a fiber. A less costly alternative to a nylon fiber is a polyester fiber. However, a surface finishing article employing a combination of a polyester fiber with a phenol-formaldehyde resin has not been commercially feasible due to the resin not adhering well to the polyester fiber, thus, resulting in a surface finishing article having insufficient strength and durability.
The combination of polyester fibers with other binders such as epoxy resins, as described in U.S. Pat. No. 2,958,593, have very good performance, but the epoxy binders are significantly more costly than phenolic resin binders and are highly reactive systems which are more difficult to process than phenolic resins. Furthermore, the epoxy binders are difficult to recycle in the manufacturing process as compared to formaldehyde resin binders. Further, epoxy resin residue is very difficult to clean up from processing equipment once it hardens and, thus, results in considerable downtime of equipment during clean up.
U.S. Pat. No. 4,794,041 describes a method for activation of polyethylene terephthalate material, such as fibers used in tire yarns, to provide enhanced adhesion to adhesives such as epoxy or isocyanate materials. The polyester material is activated by an electron beam source, which is believed by the patentee to activate the material by promotion of free radicals to generate carboxyl and hydroxyl functions. This treated surface, particularly when used in tire cords, is coated with a resorcinol-formaldehyde resin, modified-rubber latex, prior to incorporation of the fiber into tire bodies.
There are references teaching exposing polyester fibers to UV radiation to enhance adhesion to various binders. The references describe processes in which polyester fibers are subjected to high intensity UV radiation for relatively-short periods of time resulting in improved adhesion to adhesives and epoxy resins. Great Britain Pat. No. 1,228,173 (1971) describes UV treatment of polyester textile materials which is done in the presence of air or other gases. The treatment is done with relatively low intensity radiation, followed by coating the treated fibers with formaldehyde-containing adhesives. The principal objective of the treatment is to prepare polyester fibers for incorporation into rubber tire bodies.
U.S. Pat. No. 4,594,262 describes polyester film which is subjected to electron-beam radiation while passing through an inert atmosphere, such as nitrogen, to produce a surface having improved bonding to organic coatings. Great Britain Pat. No. 1,149,812 (1969) describes the UV treatment of polyester film suitable for use in photographic applications, where the polyester film is exposed to ultraviolet radiation during the biaxial stretching or the thermal setting process. The treated film has improved adhesion to coatings used in photographic film applications.
EP 81-0,043,410 (laid open Jan. 13, 1982) describes a method for priming polyester yarn with UV radiation and thereafter coating the yarn with a silane of the glycidoxy type, where the silane is applied to the fiber before or immediately after the UV radiation. After the priming step is completed, the fiber is treated with a non-ammoniated resorcinol formaldehyde latex dip. The resultant primed and coated polyester fibers are then useful for incorporation into tire cords EP 81-102,812 (laid open Jan. 13, 1982) describes a process for treating polyester fiber to enhance adhesion. The process subjects the polyester fiber to UV radiation after drawing the fiber. A fiber finish consisting of a silane, which is preferably a gamma-glycidoxy-trimethoxy-propyltrimethoxysilane, is also applied to the fiber.
The use of peroxide solutions to enhance adhesion to polyester films has been demonstrated. U.S. Pat. No. 4,051,302 describes a method of improving adhesion to polyester film surfaces where the polyester is coated with both an aqueous hydrogen peroxide solution and a hydrophilic polymer and, thereafter, the coated polyester is radiated with UV while the surface is still wet. U.S. Pat. No. 3,849,166 describes a method of generating a hydrophilic surface on polyethylene terephthalate film for photographic applications, where the film is first wet with an aqueous solution containing hydrogen peroxide and a water miscible solvent, and then the film is exposed to UV radiation while the surface was wet. U.S. Pat. No. 3,360,448, describes treating polyester film surfaces first with hydrogen peroxide followed by UV radiation for the purposes of enhancing wetability of the polyester surface to photosensitive materials.
To date, there has not been a surface finishing article which utilizes a combination of polyester fiber and a thermoset phenol-formaldehyde resin suitable for use in applications demanding high structural integrity and durability. Surface finishing articles have unique requirements of flexibility and durability which have not been addressed or solved to date by the prior art. There has also not been a method employing UV treatment of polyester fibers for use in surface finishing articles.